Industries generate large quantities of liquid, semi-solid and solid waste materials on a daily basis. As a result of this industrial activity, large masses of such materials exist which present a considerable hazard to the environment. These waste materials are often in the form of solids or highly viscous semi-solids containing hard lumps of solid material. Of particular concern are waste materials containing heavy metals which may be leached into surface water and ground water.
A number of methods for treating waste material with additives to form a physically and chemically stable end product have been proposed. Examples of such processes are disclosed in the following U.S. Pat. Nos. 4,741,776 issued May 3, 1988 to Bye, et al.; 4,600,514 issued Jul. 15, 1986 to Conner; 4,547,290 issued Oct. 15, 1985 to Pichat; 4,533,395 issued Aug. 6, 1985 to Vejmelka, et al.; 4,518,508 issued May 21, 1985 to Conner; 4,509,696 issued Apr. 9, 1985 to Donaldson; 4,432,666 issued Feb. 21, 1984 to Frey, et al.; 4,338,134 issued Jul. 6, 1982 to Graf zu Munster; 4,209,335 issued Jun. 24, 1980 to Katayama, et al.; 4,274,880 issued Jun. 23, 1981 to Chappell; 4,149,968 issued Apr. 17, 1979 to Kupiec, et al.; 3,947,284 issued Mar. 30, 1976 to Kitsugi, et al.; 3,841,102 issued Oct. 15, 1974 to Sinner, et al.; and, 3,837,872 issued Sep. 24, 1974 to Conner. For example, U.S. Pat. No. 4,509,696 to Donaldson discloses an apparatus and method for treating disposable organic waste material with an alkaline metal silicate and a setting agent. The apparatus and method disclosed in the U.S. Pat. No. 4,509,696 is not, however, adapted to treat solid waste or highly viscous semi-solid waste containing hard solid lumps of waste material. Consequently, there exists a need for an apparatus and method for mixing solid or highly viscous semi-solid waste materials with additives in order to effect the treatment of the waste materials.